/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.client;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.lang.Nullable;
import org.springframework.util.FileCopyUtils;

import java.io.IOException;
import java.nio.charset.Charset;

/**
 * Spring's default implementation of the {@link ResponseErrorHandler} interface.
 *
 * <p>This error handler checks for the status code on the {@link ClientHttpResponse}:
 * Any code with series {@link org.springframework.http.HttpStatus.Series#CLIENT_ERROR}
 * or {@link org.springframework.http.HttpStatus.Series#SERVER_ERROR} is considered to be
 * an error; this behavior can be changed by overriding the {@link #hasError(HttpStatus)}
 * method. Unknown status codes will be ignored by {@link #hasError(ClientHttpResponse)}.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @author Juergen Hoeller
 * @see RestTemplate#setErrorHandler
 * @since 3.0
 */
public class DefaultResponseErrorHandler implements ResponseErrorHandler {

    /**
     * Delegates to {@link #hasError(HttpStatus)} (for a standard status enum value) or
     * {@link #hasError(int)} (for an unknown status code) with the response status code.
     *
     *
     * 响应码是否异常 4xx,5xx
     * @see ClientHttpResponse#getRawStatusCode()
     * @see #hasError(HttpStatus)
     * @see #hasError(int)
     */
    @Override
    public boolean hasError(ClientHttpResponse response) throws IOException {
        int rawStatusCode = response.getRawStatusCode();
        HttpStatus statusCode = HttpStatus.resolve(rawStatusCode);
        return (statusCode != null ? hasError(statusCode) : hasError(rawStatusCode));
    }

    /**
     * Template method called from {@link #hasError(ClientHttpResponse)}.
     * <p>The default implementation checks {@link HttpStatus#isError()}.
     * Can be overridden in subclasses.
     *
     * @param statusCode the HTTP status code as enum value
     * @return {@code true} if the response indicates an error; {@code false} otherwise
     * @see HttpStatus#isError()
     */
    protected boolean hasError(HttpStatus statusCode) {
        return statusCode.isError();
    }

    /**
     * Template method called from {@link #hasError(ClientHttpResponse)}.
     * <p>The default implementation checks if the given status code is
     * {@code HttpStatus.Series#CLIENT_ERROR CLIENT_ERROR} or
     * {@code HttpStatus.Series#SERVER_ERROR SERVER_ERROR}.
     * Can be overridden in subclasses.
     *
     * @param unknownStatusCode the HTTP status code as raw value
     * @return {@code true} if the response indicates an error; {@code false} otherwise
     * @see HttpStatus.Series#CLIENT_ERROR
     * @see HttpStatus.Series#SERVER_ERROR
     * @since 4.3.21
     */
    protected boolean hasError(int unknownStatusCode) {
        HttpStatus.Series series = HttpStatus.Series.resolve(unknownStatusCode);
        return (series == HttpStatus.Series.CLIENT_ERROR || series == HttpStatus.Series.SERVER_ERROR);
    }

    /**
     * Delegates to {@link #handleError(ClientHttpResponse, HttpStatus)} with the
     * response status code.
     *
     * @throws UnknownHttpStatusCodeException in case of an unresolvable status code
     * @see #handleError(ClientHttpResponse, HttpStatus)
     */
    @Override
    public void handleError(ClientHttpResponse response) throws IOException {
        HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
        if (statusCode == null) {
            throw new UnknownHttpStatusCodeException(response.getRawStatusCode(), response.getStatusText(),
                    response.getHeaders(), getResponseBody(response), getCharset(response));
        }
        handleError(response, statusCode);
    }

    /**
     * Handle the error in the given response with the given resolved status code.
     * <p>The default implementation throws an {@link HttpClientErrorException}
     * if the status code is {@link HttpStatus.Series#CLIENT_ERROR}, an
     * {@link HttpServerErrorException} if it is {@link HttpStatus.Series#SERVER_ERROR},
     * and an {@link UnknownHttpStatusCodeException} in other cases.
     *
     * @see HttpClientErrorException#create
     * @see HttpServerErrorException#create
     * @since 5.0
     */
    protected void handleError(ClientHttpResponse response, HttpStatus statusCode) throws IOException {
        String statusText = response.getStatusText();
        HttpHeaders headers = response.getHeaders();
        byte[] body = getResponseBody(response);
        Charset charset = getCharset(response);
        switch (statusCode.series()) {
            case CLIENT_ERROR:
                // 客户端错误处理
                throw HttpClientErrorException.create(statusCode, statusText, headers, body, charset);
            case SERVER_ERROR:
                // 服务端错误处理
                throw HttpServerErrorException.create(statusCode, statusText, headers, body, charset);
            default:
                throw new UnknownHttpStatusCodeException(statusCode.value(), statusText, headers, body, charset);
        }

    }

    /**
     * Determine the HTTP status of the given response.
     *
     * @param response the response to inspect
     * @return the associated HTTP status
     * @throws IOException                    in case of I/O errors
     * @throws UnknownHttpStatusCodeException in case of an unknown status code
     *                                        that cannot be represented with the {@link HttpStatus} enum
     * @since 4.3.8
     * @deprecated as of 5.0, in favor of {@link #handleError(ClientHttpResponse, HttpStatus)}
     */
    @Deprecated
    protected HttpStatus getHttpStatusCode(ClientHttpResponse response) throws IOException {
        HttpStatus statusCode = HttpStatus.resolve(response.getRawStatusCode());
        if (statusCode == null) {
            throw new UnknownHttpStatusCodeException(response.getRawStatusCode(), response.getStatusText(),
                    response.getHeaders(), getResponseBody(response), getCharset(response));
        }
        return statusCode;
    }

    /**
     * Read the body of the given response (for inclusion in a status exception).
     *
     * @param response the response to inspect
     * @return the response body as a byte array,
     * or an empty byte array if the body could not be read
     * @since 4.3.8
     */
    protected byte[] getResponseBody(ClientHttpResponse response) {
        try {
            return FileCopyUtils.copyToByteArray(response.getBody());
        }
        catch (IOException ex) {
            // ignore
        }
        return new byte[0];
    }

    /**
     * Determine the charset of the response (for inclusion in a status exception).
     *
     * @param response the response to inspect
     * @return the associated charset, or {@code null} if none
     * @since 4.3.8
     */
    @Nullable
    protected Charset getCharset(ClientHttpResponse response) {
        HttpHeaders headers = response.getHeaders();
        MediaType contentType = headers.getContentType();
        return (contentType != null ? contentType.getCharset() : null);
    }

}
